This invention relates to dyes, to inks and to their use in ink jet printing.
Ink jet printing methods involve printing an image onto a substrate using ink droplets emitted from a small nozzle without bringing the nozzle into contact with the substrate. Over recent years ink jet printers have become popular because they are quieter and more versatile than impact printers, for example conventional basket typewriters are noisy and the images they can print are restricted to the shapes moulded onto the end of each mechanical lever. The most popular ink jet printers are the thermal and piezoelectric.
The requirements for inks used in ink jet printers include:
i) they should not clog the small nozzle from which they are emitted, or form a blocking crust over the end,
ii) the resultant image should have good water-fastness so that it does not smudge excessively on contact with sweat or water,
iii) the image should also have a good light-fastness so that it does not fade quickly on exposure to daylight,
iv) they should dry quickly on paper and give discrete, sharp images,
v) they should have good storage stability, and
vi) they should have a high colour strength to give intensely coloured images.
WO91/06608 describes aqueous inks containing a polyester, water, a pigment and a wax. Whilst these inks are useful in printing presses, the pigments they contain require intensive and expensive milling to make them fine enough to pass through ink jet printer heads and the pigments have a tendency to settle out from the ink on standing for long periods. Furthermore, images formed from inks containing insoluble pigments are generally opaque and dull, limiting their usefulness on overhead projector slides.
There is a need for dyes and inks which have good storage stability, a high colour strength and produce images having a high light-fastness and water-fastness when printed on a substrate.
According a first aspect of the present invention there is provided a dye of the Formula (1) and tautomers thereof: 
wherein:
A is optionally substituted phenyl;
R1 is methyl;
R2 is H, CN, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted-alkynyl, optionally substituted aryl or a carbonamido group; and
R3 is an optionally substituted 5- or 6-membered ring.
In a first preferred embodiment A is phenyl or mono substituted phenyl, more preferably mono substituted phenyl.
In a second preferred embodiment A is di-, tri-, tetra- or penta-substituted phenyl.
When R2 is optionally substituted alkyl, alkenyl or alkynyl it is preferably optionally substituted C1-12-alkyl, C1-12-alkenyl or C1-12-alkynyl, more preferably optionally substituted C1-12-alkyl, especially C1-4-alkyl; more especially methyl:
When R2 is optionally substituted aryl it is preferably optionally substituted phenyl.
R2 is preferably CN or a carbonamido group. A preferred carbonamido group is of the formula CONHR4 wherein R4 is H or optionally substituted alkyl or aryl.
R4 is preferably optionally substituted C1-6-alkyl or optionally substituted phenyl, more preferably C1-4-alkyl.
R3 is preferably an optionally substituted 5- or 6-membered ring comprising carbon atoms and optionally one or two atoms selected from O, N and S, more preferably one O or S atom and four or five carbon atoms. R3is more preferably optionally substituted phenyl, cyclohexyl, cyclopentyl, furanyl, tetrahydrofuranyl, pyranyl, dihydropyranyl or tetrahydropyranyl. Still more preferably, R3 is optionally substituted furanyl or tetrahydrofuranyl, especially optionally substituted tetrahydrofuranyl.
Examples of groups represented by R3 include furan-2-yl, tetrahydrofuran-2-yl, furan-3-yl, tetrahydrofuran-3-yl, pyran-2-yl, pyran-3-yl, pyran-4-yl, dihydropyran-2-yl, dihydropyran-3-yl, dihydropyran-4-yl, tetrahydropyran-2-yl, tetrahydropyran-3-yl and tetrahydropyran-4-yl.
In one preferred embodiment at least one of the substituents on A is a hypsochromic substituent. A hypsochromic substituent is a substituent which causes a shift in the absorption maximum of the dye to a shorter wavelength relative to a dye which is identical in every respect except that in place of the substituent there is a hydrogen atom, as measured in CH2Cl2 at 20xc2x0 C.
Preferred substituents, most of which are hypsochromic, on A are of the formula CO2R5, OCOR5, COR5, COCOR5, SO2R5, SO2NH2, SO2NR5R6, SOR5, SO2OR5, CN, CONR5R6, CONH2 and CF3; wherein each R5 independently is optionally substituted phenyl or optionally substituted alkyl which is optionally interrupted by one or more oxygen, sulphur or nitrogen atoms; and each R6 independently is H or a substituent as defined for R5; or R5 and R6 together with the nitrogen to which they are attached form a 5 or 6 membered ring.
Especially preferred hypsochromic substituents are of the formula CO2R7 and CONHR7 wherein each R7 independently is [(CH2) mO]nR8, m is 2 or 3, n is 1, 2, 3 or 4 and R8 is H or C1-4-alkyl.
The optional substituents present on A may also be selected from NHCOR5, wherein R5 is as hereinbefore defined; alkoxy, preferably C1-4-alkoxy; alkyl, preferably C1-4-alkyl; halo, preferably Cl or F; nitro; hydroxy; and optionally substituted amino, preferably xe2x80x94NRaRb wherein Ra and Rb each independently H, C1-4-alkyl or C1-4-alkyl substituted by hydroxy, carboxy or sulpho.
When R5 and R6 together with the nitrogen to which they are attached form a 5 or 6 membered ring it is preferably optionally substituted morpholine, piperazine, piperidine, piperidone or piperidone monohydrate, more preferably 4-piperidone or 4-piperidone monohydrate.
Preferably R5 is optionally substituted phenyl, optionally substituted C1-4-alkyl or R7 wherein R7 is as hereinbefore defined.
Preferably R6 is H or optionally substituted C1-4-alkyl, more preferably H.
The optional substituents which may be present on R2, R3, R4 and R5 are preferably selected from C1-4-alkoxy, especially methoxy; halo, especially Cl, Br or F; C1-4-alkyl, especially methyl; nitro; cyano; CF3 hydroxy; optionally substituted amino, especially xe2x80x94NRaRb wherein Ra and Rb are each independently H, C1-4-alkyl or C1-4-alkyl substituted by hydroxy, carboxy or sulpho; amido, especially xe2x80x94CONRaRb wherein Ra and Rb are as hereinbefore defined; or ester, especially xe2x80x94CO2Ra wherein Ra is as hereinbefore defined other than H.
Preferably in the dyes according to the first preferred embodiment of the invention A is phenyl carrying one group of the formula CO2R7 wherein R7 is as hereinbefore defined.
Preferably in the dyes according to the second preferred embodiment of the invention A carries a total of 2, 3, 4 or 5 substituents, more preferably 2 or 3 substituents, especially 2 substituents.
More preferably in the dyes of the second preferred embodiment A is phenyl carrying two, more preferably one hypsochromic substituent, and two, more preferably one of the alternative substituents mentioned above.
In view of the foregoing preferences a preferred dye of Formula (1) is of the Formula (2) and tautomers thereof: 
wherein:
each hyp independently is a group of the formula CO2R5, OCOR5, COR5, COCOR5, SO2R5, SO2NHR5, SO2NH2, SO2NR5R5, SO2OR5, CN, CONHR5, CF3,CONHR7 or CO2R7;
each R9 independently is alkoxy (preferably C1-4-alkoxy), halo, alkyl (preferably C1-4-alkyl), nitro, hydroxy or optionally substituted amino;
r is 0, 1 or 2;
q is 0, 1, or 2;
(r+q) is 1, 2, 3 or 4; and
R1, R2, R3, R7 and each R5 independently are as hereinbefore defined.
Preferably R2 in Formula (2) is CN or CONHR4 wherein R4 is as hereinbefore defined.
Preferably R3 in Formula (2) is optionally substituted furanyl or tetrahydrofuranyl, more preferably furanyl or tetrahydrofuranyl.
Preferably R5 in Formula (2) is phenyl or C1-4-alkyl.
Each hyp in Formula (2) is preferably independently CONHR7 or CO2R7.
Preferably each R9 is C1-4-alkoxy, C1-4-alkyl or halo (especially Cl).
Preferred dyes according to the first preferred embodiment of the invention are of the Formula (2) wherein r is 0 or 1; q is 0 or 1 and (r+q) is 1. More preferably q is 0; r is 1; hyp is CO2R7; R1 is methyl; R2 is CN; R3 is furanyl or tetrahydrofuranyl, especially tetrahydrofuranyl; and R7 is as defined above.
Preferred dyes according to the second preferred embodiment of the invention are of the Formula (2) wherein (r+q) is 2, 3 or 4, more preferably 2. More preferably r is 0; q is 2; R9 is selected from alkyl and alkoxy (especially C1-4-alkyl and C1-4-alkoxy); R1 is methyl; R2 is CN; and R3 is furanyl or tetrahydrofuranyl, especially tetrahydrofuranyl.
Preferably the dyes of Formulae (1) and (2) are free from sulpho and carboxy groups.
Dyes of Formula (1) may be prepared diazotising a compound of formula Axe2x80x94NH2 and coupling the resultant diazonium salt to a compound of Formula (3): 
wherein R1, R2, R3 and A are as hereinbefore defined.
The diazotisation is preferably performed at a temperature below 6xc2x0 C., e.g. xe2x88x925xc2x0 C. to +5xc2x0 C. Typically nitrous acid is used as the diazotising agent and the process is performed in the presence of dilute mineral acid, for example dilute hydrochloric acid.
Compounds of Formula (3) may be prepared by condensing an amine of the formula. R3xe2x80x94CH2xe2x80x94NH2 with a suitable acetates and acetoacetates.
Dyes of Formula (1) exist in tautomeric forms other than that shown above and these tautomers are included in the present invention. For example the azo xe2x80x94Nxe2x95x90Nxe2x80x94 group can tautomerise to a xe2x80x94NHxe2x80x94Nxe2x95x90 group and, indeed, the hydrazo from is believed to predominate over the azo form.
The dyes of Formula (1) are particularly valuable for the preparation of water-based polymeric inks for ink jet printing. Accordingly a second feature of the invention provides an ink comprising an aqueous medium, a water-dissipatable polymer and a dye of Formula (1) as hereinbefore defined.
The water-dissipatable polymer preferably bears ionised carboxy and/or sulphonate groups, especially ionised sulphonate groups, because these assist water dissipatability of the polymer. Such groups can be chain pendant and/or terminal.
The water-dissipatable polymer is preferably a water-dissipatable polyester. The water-dissipatable polyester can be prepared using conventional polymerisation procedures known to be effective for polyester synthesis. Thus, it is well known that polyesters contain carbonyloxy (i.e xe2x80x94C(xe2x95x90O)xe2x80x94Oxe2x80x94) linking groups and may be prepared by a condensation polymerisation process in which an acid component (including ester-forming derivatives thereof) is reacted with a hydroxyl component. The acid component may be selected from one or more polybasic carboxylic acids, e.g. di- and tri-carboxylic acids or ester-forming derivatives thereof, for example acid halides, anhydrides or esters. The hydroxyl component may be one or more polyhydric alcohols or phenols (polyols), for example, diols, triols, etc. (It is to be understood, however, that the polyester may contain, if desired, a proportion of carbonylamino linking groups xe2x80x94C(xe2x95x90O)xe2x80x94NHxe2x80x94 (i.e. amide linking groups) by including an appropriate amino functional reactant as part of the xe2x80x9chydroxyl componentxe2x80x9d; such as amide linkages). The reaction to form a polyester may be conducted in one or more stages. It is also possible to introduce in-chain unsaturation into the polyester by, for example, employing as part of the acid component an olefinically unsaturated dicarboxylic acid or anhydride.
Polyesters bearing ionised-sulphonate groups may be prepared by using at least one monomer having two or:more functional groups which will readily undergo an ester condensation reaction (e.g. carboxyl groups, hydroxyl groups or esterifiable derivatives thereof) and one or more sulphonic acid groups (for subsequent neutralisation after polyester formation) or ionised sulphonate groups (i.e. neutralisation of the sulphonic acid groups already having been effected in the monomer) in the synthesis of the polyester. In some cases it is not necessary to neutralise sulphonic acid groups since they may be sufficiently strong acid groups as to be considerably ionised in water even without the addition of base. Often, the sulphonic acid or ionised sulphonate containing monomer is a dicarboxylic acid monomer having at least one ionised sulphonate substituent (thereby avoiding any need to effect neutralisation subsequent to polyester formation). (Alternatively, alkyl carboxylic acid ester groups may be used in place of the carboxylic acid groups as ester-forming groups). Such a monomer will therefore be part of the acid component used in the polyester synthesis.
Preferred polybasic carboxylic acids which can be used to form the polyester have two or three carboxylic acid groups. For example, one can use C4 to C20 aliphatic, alicyclic and aromatic compounds having two or more carboxy groups and their ester forming derivatives (e.g. esters, anhydrides and acid chlorides), and dimer acids such as C36 dimer acids. Specific examples include adipic acid, fumaric acid, maleic acid, succinic acid, itaconic acid, sebacic acid, nonanedioic acid, decanedioic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid and tetrahydrophthalic acid and their acid chlorides. Anhydrides include succinic, maleic, phthalic and hexahydrophthalic anhydrides.
Preferred polyols which can be used to form the polyester include those having from 2 to 6, more preferably 2 to 4 and especially 2 hydroxyl groups per molecule. Suitable polyols having two hydroxy groups per molecule include diols such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), the 1,2-, 1,3- and 1,4-cyclohexanediols and the corresponding cyclohexane dimethanols, diethylene glycol, dipropylene glycol, and diols such as alkoxylated bisphenol A products, e.g. ethoxylated or propoxylated bisphenol A. Suitable polyols having three hydroxy groups per molecule include triols such as trimethylolpropane (1,1,1-tris (hydroxymethyl)ethane). Suitable polyols having four or more hydroxy groups per molecule include pentaerythritol (2,2-bis(hydroxymethyl)-1,3-propanediol) and sorbitol (1,2,3,4,5,6-hexahydroxyhexane).
Compounds having two or more groups which readily undergo an ester condensation reaction and have one or more sulphonate groups are dicarboxylic acid monomers having at least one ionised sulphonate group. Examples of such compounds are aromatic dicarboxylic acids having an ionised sulphonate group, for example those of the formula: 
wherein M is a cation (preferably sodium, lithium or potassium); and each Rc independently is H, a cation or C1-4-alkyl (preferably methyl or ethyl). Preferred compounds of the above formula are of formula: 
wherein M and Rc are as defined above. Particularly preferred is the mono sodium salt, this material being known as sodio-5-sulphoisophthalic acid (SSIPA).
Other useful compounds which have two or more groups which readily undergo an ester condensation reaction and have one or more sulphonate groups are dihydroxy monomers having at least one sulphonate group, especially those of the formula: 
wherein M is as hereinbefore defined above and each Rd independently is alkylene, preferably C2-4-alkylene. Preferred compounds of the above formula are: 
wherein M is as hereinbefore defined.
Polyesters bearing ionised carboxy groups can be prepared by various means. For example, if the hydroxyl component of the reactants is stoichiometrically in excess of the acid component, a hydroxyl-terminated polyester can be formed, which may be subsequently converted to a carboxy terminated polyester by wholly or partially reacting the hydroxyl groups with an appropriate reagent (e.g. an acid anhydride or a dicarboxylic acid). Alternatively, terminal carboxy functionality may be directly introduced by employing an appropriate stoichiometric excess of the acid component reactants. In another alternative, chain-pendant carboxy groups may be introduced by using reagents such as dimethylol propionic acid (DMPA) since if appropriate reaction condition are employed (e.g. polymerisation temperature below 150xc2x0 C.) the hindered carboxy group thereof does not take part to any significant extent in the ester-forming reactions during the polyester synthesis and the DMPA effectively behaves as a simple diol. Chain-pendant and/or terminal carboxy groups could also be introduced by employing a tri- or higher functionality carboxylic acid or anhydride in the polyester synthesis, for example, trimellitic acid or anhydride. Combinations of the above procedures could also be used. It is thus seen that terminal or side-chain carboxy groups or both can be introduced as desired. These can be fully or partially neutralised with an appropriate base to yield ionised carboxy groups. The counter ions used may be as for the ionised sulphonate groups described above (apart from H+ since the carboxylic acid groups themselves are normally insufficiently ionised to provide a significant amount of ionised carboxy groupsxe2x80x94although F substituents would increase acid strength), with alkali metal ions such as Na+, Li+ and K+ again being particularly preferred, and ammonium and organic amine derived cations less preferred because some have an undesirable odour.
The water-dissipatable polyester may optionally have hydrophilic non-ionic segments, for example within the polyester backbone (i.e. in-chain incorporation) or as chain-pendant or terminal groups. Such groups may act to contribute to the dispersion stability or even water-solubility of the polyester. For example, polyethylene oxide chains may be introduced into the polyester during its synthesis by using as part of the hydroxyl component, ethylene oxide-containing mono, di or higher functional hydroxy compounds, especially polyethlene glycols and alkyl ethers of polyethylene glycols, examples of which include:
Rexe2x80x94Oxe2x80x94(CH2CH2O)nxe2x80x94H
HOxe2x80x94(CH2CH2O)nxe2x80x94H

wherein Re is C1-20-alkyl, preferably C1-4-alkyl, more preferably methyl; n is 1 to 500; and p is 1 to 100.
A small segment of a polyethylene oxide chain could be replaced by a propylene oxide or butylene oxide chainin such non-ionic groups, but should still contain ethylene oxide as a major part of the chain.
The amount of ionised sulphonate and/or carboxy groups present in the polyester should be sufficient to provide or contribute to water-dissipatability of the polyester, although it should not be so high as to render the resulting polyester unacceptably water-sensitive. This amount will depend, inter alia, on factors such as the hydrophilicity/hydrophobicity of units provided by other monomers in the polyester synthesis or any surfactants (if used), and also the relative proportions of ionised sulphonate/carboxy groups. With regard to the last mentioned point, ionised sulphonate groups are more effective at providing or contributing to water-dissipatability than ionised carboxy groups and so can be used at considerably lower levels in comparison to ionised carboxy groups.
If the polyester is wholly or predominantly sulphonate stabilised (by which is meant the water dissipatability-providing groups are provided wholly or predominately by ionised sulphonate groups). The ionised sulphonate group content is preferably within the range from 7.5 to 100 milliequivalents (more preferably 10 to 75 milliequivalents and particularly 11 to 56 milliequivalents) per 100 g of polyester. When using SSIPA as the monomer for providing the ionised sulphonate groups, the amount of this monomer used in the polyester synthesis, based on the weight of all the monomers used in the polyester synthesis, will usually be within the range from 2 to 20% by weight (more usually 3 to 15% by weight). The carboxylic acid value (AV) of the polyester which is predominantly sulphonate stabilised, i.e. an AV based on the carboxylic acid groups only (i.e. excluding sulphonate groups) will generally be within the range of from 0 to 100 mgKOH/g, more preferably 0 to 50 mgKOH/g, especially 0 to 25 mgKOH/g, more especially 0 to 10 mgKOH/g.
If the polyester is predominantly stabilised by ionised carboxy groups, the carboxylic acid value AV of the polyester is preferably within the range of from 20 to 140 mgKOH/g (more preferably 30 to 100 mgKOH/g).
Usually, the polyester is either predominantly sulphonate-stabilised or predominantly carboxylate stabilised (preferably the former).
If the polyester contains polyethylene oxide chains, the polyethylene oxide chain content should preferably not exceed 25% by weight (and more preferably should not exceed 15% by weight), based on the total weight of the polyester, in order to avoid unacceptable water-sensitivity. Therefore the amount is preferably 0 to 25% by weight (more preferably 0 to 15% by weight) based on the total weight of polyester.
The water-dissipatable polyester preferably has a number average molecular weight Mn of up to 30,000. The Mn is preferably in the range from 500 to 30,000, more preferably 1000 to 25,000, especially 2000 to 20,000. These Mn lead to particularly good storage stability for the resultant inks. The measurement of Mn is well known to those. skilled in the art, and may for example be effected using gel permeation chromatography in conjunction with a standard polymer such as polystyrene or polymethylmethacrylate of known molecular weight.
The water-dissipatable polyester preferably has a hydroxyl number of from 0 to 225 mg KOH/g, more preferably 0 to 125 mg KOH/g, especially from 0 to 50 mgKOH/g.
The Tg of the water-dissipatable polyester (i.e. the temperature at which the polymer changes from a glassy, brittle state to a plastic, rubbery state) is preferably in the range xe2x88x9238xc2x0 C. to 105xc2x0 C., more preferably xe2x88x9220 to 70xc2x0 C., especially xe2x88x9210xc2x0 C. to 60xc2x0 C.
The esterification polymerisation processes for making the polyesters for use in invention composition are known and need not be described here in more detail. Suffice to say that they are normally carried out in the melt using catalysts, for example a tin-based catalyst, and with the provision for removing any water or alcohol formed from the condensation reaction.
The water-dissipatable polyester may be dissipated in water by adding the solidified melt directly into water. The solidified melt is preferably in a form such as flake (which can often be obtained directly from the melt) or communised solid (obtained for example by grinding). Alternatively, water can be added directly to the hot polyester melt until the desired solids content/viscosity is reached. Still further, the polyester may be dissipated in water by adding an aqueous pre-dissipation (or organic solvent solution) of the polyester to the water phase.
The water-dissipatable polyesters normally do not need an external surfactant when being dissipated into water, although such surfactants may be used to assist the dissipation if desired and in some cases can be useful in this respect because additional surfactants reduce the required amount of dissipating groups (i.e. sulphonate, and (mono alkoxy)polyalkylene chains if used).
Water-dissipatable polyesters can also be purchased from Eastman Kodak Company and Zeneca Limited. Examples include Eastman AQ29D and AQ55W.
The water-dissipatable polymer may also be formed by performing free radical polymerisation of olefinically unsaturated monomers in the presence of a polyester. This gives what could be called a polyester-acrylic hybrid. Olefinically unsaturated monomers which can be used include olefinically unsaturated carboxy functional monomers, e.g. acrylic acid, methacrylic acid, fumaric acid, itaconic acid and xcex2-carboxyethyl acrylate; olefinically unsaturated monomers which are free from carboxy and hydroxy groups, e.g. 1,3-butadiene, isoprene, styrene, vinylidene halides, vinylidene esters and esters of acrylic acid and methacrylic acid, e.g. methyl (meth) acrylate, ethyl (meth)acrylate n-butyl (meth)acrylate and 2-ethyl hexyl (meth)acrylate; and olefinically unsaturated monomers having a hydroxy group e.g. N-methylol (meth)acrylamide and hydroxy C2-8-alkyl esters of (meth)acrylic acid. If the polyester has been prepared using a component which has unsaturation therein, e.g. fumaric acid, maleic acid or muconic acid or allyl-containing dihydroxy or dicarboxy compounds, the product from the polyesterification reaction will have unsaturation incorporated into its structure which can take part in the free radical polymerisation to give a graft copolymer. The free radical polymerisation processes use a free-radical generating initiator system such as (for example) the redox radical initiator system tertiary butylhydroxide/isoascorbic acid and will take place in the aqueous phase, rather than in the melt. However, excessive amounts of acrylic polymer (whether formed in the presence of polyester which has unsaturation or is free from unsaturation) often leads to a deterioration in ink properties and it is preferred that no acrylic polymer is present or, if its is present, the amount is less than 40%, preferably less than 30%, more preferably less than 10% by weight relative to the weight of polyester.
Preferably the aqueous medium is water or a mixture of water and one or more organic solvent, more preferably a mixture comprising water, one or more water-immiscible organic solvent and one or more water-miscible organic solvent.
Preferred dyes in the ink are the preferred dyes according to the first aspect of the invention, more preferably the dyes of the Formula (2).
Preferably the dye of Formula (1) dyes the water-dissipatable polymer to give a coloured water-dissipatable polymer in the ink. The water-dissipatable polymer may be dyed prior to inclusion in the ink or may be dyed during the preparation of the ink.
The water-dissipatable polymer may be dyed by heating a water-dissipatable polymer and a dye of Formula (1) at an elevated temperature, for example at a temperature in the range 35 to 150xc2x0 C., preferably from 40 to 90xc2x0 C. Simply mixing the dye and polymer in water at room temperature leads to a slight up-take of colour but heating is usually necessary for a full dyeing.
Preferably inks according to the invention are prepared by mixing together (i) a solution of a dye of Formula (1) in a water-immiscible solvent and (ii) a mixture of a water-dissipatable polymer, water-miscible solvent and optionally water. Equally the inks may be prepared by mixing together (i) a solution of a dye of Formula (1) in a mixture of a water-miscible solvent and a water-immiscible solvent and (ii) a water-dissipatable polymer and optionally water. In either case, if there is no water in component (ii) the water may be added to the mixture of (i) a (ii) subsequently to give an ink according to the invention. However it is preferred for component (ii) to contain water. These processes lead to particularly good up-take of dye by the polymer to give intensely coloured inks.
The amount of dye and water-dissipatable polymer contained in the ink will vary according to the depth of shade required. Typically, however, the ink will comprise:
(a) from 0.5 to 10 parts, more preferably 1 to 5 parts of a dye of Formula (1) (or more preferably of Formula (2));
(b) from 2 to 25 parts, more preferably 5 to 15 parts of a water-dissipatable polymer (preferably a water-dissipatable polyester);
(c) from 40 to 90 parts, more preferably from 50 to 80 parts of water; and
(d) from 0 to 60 parts, more preferably 5 to 40 parts of organic solvent; wherein all parts are by weight and the total number of parts of (a)+(b)+(c)+(d) add up to 100.
The number of parts of the water-dissipatable polymer is calculated on a 100% solids basis. For example 50 g of a 20% solids polymer is taken as 10 g of polymer.
As hereinbefore mentioned, the ink may contain an organic solvent (e.g. component (d) above) and this may be a mixture of organic solvents. In a preferred embodiment the ink contains an organic solvent consisting of a water-miscible organic solvent and a water-immiscible organic solvent.
Suitable water-immiscible organic solvents include aromatic hydrocarbons, e.g. toluene, xylene, naphthalene, tetrahydronaphthalene and methyl naphthalene; chlorinated aromatic hydrocarbons, e.g. chlorobenzene, fluorobenzene, chloronaphthalene and bromonaphthalene; esters, e.g. butyl acetate, ethyl acetate, methyl benzoate, ethyl benzoate, benzyl benzoate, butyl benzoate, phenylethyl acetate, butyl lactate, benzyl lactate, diethyleneglycol dipropionate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di (2-ethylhexyl) phthalate; alcohols having six or more carbon atoms, e.g. hexanol, octanol, benzyl alcohol, phenyl ethanol, phenoxy ethanol, phenoxy propanol and phenoxy butanol; C5-14 ethers, e.g. anisole and phenetole; nitrocellulose, cellulose ether, cellulose acetate; low odour petroleum distillates; turpentine; white spirits; naphtha; isopropylbiphenyl; terpene; vegetable oil; mineral oil; essential oil; and natural oil; and mixtures of any two or more thereof. Benzyl alcohol is especially preferred.
Suitable water-miscible organic solvents include C1-5-alkanols, e.g. methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol and isobutanol; amides, e.g. dimethylformamide and dimethylacetamide; ketones and ketone alcohols, e.g. acetone and diacetone alcohol; C2-4-ether, e.g. tetrahydrofuran and dioxane; alkylene glycols or thioglycols containing a C2-C6 alkylene group, e.g. ethylene glycol, propylene glycol, butylene glycol, pentylene glycol and hexylene glycol; poly(alkylene-glycol)s and thioglycol)s, e.g. diethylene glycol, thiodiglycol, polyethylene glycol and polypropylene glycol; polyols, e.g. glycerol and 1,2,6-hexanetriol; and lower alkyl glycol and polyglycol ethers, e.g. 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy) ethanol, 2-(2-butoxyethoxy)ethanol, 3-butoxypropan-1-ol, 2-[2-(2-methoxyethoxy)-ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)ethoxy]-ethanol; cyclic esters and cyclic amides, e.g. optionally substituted pyrrolidones; sulpholane; and mixtures containing two or more of the aforementioned water-miscible organic solvents. Preferred water-miscible organic solvents are C1-6-alkyl mono ethers of C2-6-alkylene glycols and C1-6-alkyl mono ethers of poly(C2-6-alkylene glycols).
Component (d) of the above mentioned inks preferably comprises;
(i) 5 to 50% of a water-immiscible alcohol having at least six carbon atoms, (especially benzyl alcohol); and
(ii) 50 to 95% of a water-miscible solvent comprising
(a) a cyclic ester or cyclic amide (especially an optionally substituted pyrrolidone);
(b) a water-miscible C1-6-alkyl mono ether of a C2-6-alkylene glycol or C1-6-alkyl mono ether of poly(C2-6-alkylene glycol); or
(c) a mixture of (a) and (b).
wherein all % are by weight and add up to 100%.
The water-immiscible solvent preferably has a solubility in water at 20xc2x0 C. of up to 50 g/l. The water-miscible solvent preferably has a solubility in water at 20xc2x0 C. of more than 50 g/l.
The preferred optionally substituted pyrrolidones, are 2-pyrrolidone, dimethyl pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and N-(2-hydroxyethyl)-2-pyrrolidone and mixtures thereof.
The ratio of water-miscible organic solvent to water-immiscible organic solvent is preferably 19:1 to 1:1, more preferably 8:1 to 1:1, especially 5:1 to 1:1.
Dyes of Formula (1) have advantages over the use of pigments in that less dye is usually required than would be the case for a pigment, expensive milling is avoided, the inks are less likely to form a precipitate on standing, a far greater variety of shades are available and the resultant prints have good transparency. The latter quality is particularly important for the production of coloured substrates which require transparency, for example over-head projector slides and colour filters used in LCD television screens. The inks and dyes of the present invention also benefit from good light- and water-fastness.
A valuable feature of the invention is the low tendency for blocking the nozzles of thermal ink jet printers. Many other water dispersible polymer inks work poorly or even not at all in thermal printers. Inks of the invention form discrete droplets on the substrate with little tendency for diffusing. Consequently sharp images can be obtained, resulting in excellent print quality and little if any bleed between colours printed side-by side.
According to a third aspect of the present invention there is provided a process for printing an image on a substrate comprising applying thereto an ink containing a dye of the Formula (1) by means of an ink jet printer.
Preferred inks for use in the present process comprise an aqueous medium, a water-dissipatable polymer and a dye of Formula (1) as hereinbefore defined. Especially preferred inks for use in the process are the preferred inks according to the second aspect of the present invention.
The ink jet printer emits droplets of the ink onto a substrate from a nozzle without bringing the nozzle into contact with the substrate. Preferably the ink jet printer is a thermal or piezoelectric ink jet printer.
The substrate is preferably a paper, an overhead projector slide or a textile material. Preferred textile materials are cotton, polyester and blends thereof.
Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Examples of commercially available treated papers include HP Premium Coated Paper (available from Hewlett Packard Inc), HP Photopaper (available from Hewlett Packard Inc), Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film (available from Seiko Epson Corp.), Epson Photo Quality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper (available from Canon), Canon GP 201 Glossy Paper (available from Canon), and Canon HG 101 High Gloss Film (available from Canon).
When the substrate is a textile material the process for printing an image thereon according to the invention preferably further comprises the step of heating the resultant printed textile, preferably to a temperature of 50xc2x0 C. to 250xc2x0 C.
The inks of the present invention may also be used for the preparation of colour filters, for example those used in flat bed displays.
A fourth aspect of the present invention provides a paper, an overhead projector slide or a textile material printed with an ink according to the second aspect of the present invention or by means of a process according to the third aspect of the present invention.
A fifth aspect of the present invention provides an ink jet printer cartridge containing an ink according to the second aspect of the present invention.
Preferred Papers
The invention is further illustrated by the following examples in which all parts and percentages are by weight unless specified otherwise. In these Examples the following abbreviations are used:
Paper XA is Xerox 4024 from Rank Xerox.
Paper GB is Gilbert Bond paper from the Mead Corporation.
Paper WC is Wiggins Conqueror High White Wove 100 g/m2 from Arjo Wiggins Ltd.
xe2x80x9cxe2x88x92xe2x80x9d means not measured.
To a glass reactor fitted with distillation column and condenser were charged ingredients A, B, D, F, G and 50% of C and 50% of H. The contents were heated with stirring to a reaction temperature of 210xc2x0 C. until the mixture was clear and the acid value was  less than 10 mgKOH/g. At this point E and the remainder of C and H were charged and the temperature raised to 230xc2x0 C. The reaction was continued under reduced pressure until an acid value of 5.3 mgKOH/g was obtained. The resin was further characterised by a hydroxyl value=27.6 mgKOHg, ICI Cone and Plate viscosity @125xc2x0 C.=80 poises and a Tg (onset)=25.4xc2x0 C. and a number average molecular weight by end group analysis of approximately 2000. The resin was readily dispersed in warm distilled water to give a clear solution having a solids content of 20% w/w (hereinafter xe2x80x9cResin 1xe2x80x9d).
To a glass reactor fitted with distillation column and condenser were charged ingredients A, B, C, E, G, H and 50% of D and 50% of I. The contents were heated with stirring to a reaction temperature of 210xc2x0 C. until the mixture was clear and the acid value was 1.25 mgKOH/g. At this point F and the remainder of D and I were charged and the temperature raised to 230xc2x0 C. The reaction was continued under reduced pressure until an acid value of 2.8 mgKOH/g was obtained. The resin was further characterised by a hydroxyl value=19.7 mgKOH/g, ICI Cone and Plate viscosity @125xc2x0 C.=90 poises and a Tg (onset)=4xc2x0 C. The resin was readily dispersed in warm distilled water to give a clear solution having a solids content of 20% w/w. (hereinafter xe2x80x9cResin 2xe2x80x9d).
To a glass reactor fitted with distillation column and condenser were charged ingredients A, B, D, E, F, G and 50% of C and 50% of H. The contents were heated with stirring to a reaction temperature of 210xc2x0 C. until the mixture was clear and the acid value was  less than 10 mgKOH/g. At this point the remainder of C and H were charged and the temperature raised to 230xc2x0 C. The reaction was continued under reduced pressure until an acid value of 9.4 mgKOH/g was obtained. The resin was further characterised by a hydroxyl value=12.8 mgKOHg, ICI Cone and Plate Viscosity @125xc2x0 C.= greater than 500 poises and a Tg (onset)=18xc2x0 C. The number average molecular weight as determined by gel permeation chromatography (PS Equivalents) was 1800. The resin was readily dispersed in warm distilled water to give a clear solution having a solids content of 20% w/w (hereinafter xe2x80x9cResin 3xe2x80x9d).